1. Department of Chemistry, Nanoscience Center, University of Jyväskylä, P.O. Box 35 (YN), FI-40014 Jyväskylä, Finland
2. Department of Electrical Engineering and Automation, Aalto University, FIN-02150 Espoo, Finland
3. Department of Chemistry, University of Copenhagen, 2100 Copenhagen Ø, Denmark
4. Department of Physics,Nanoscience Center, University of Jyväskylä, P.O. Box
35 (YN), FI-40014 Jyväskylä, Finland